Aging is a risk factor for development of osteoporosis and oral bone loss. To study this situation, a good animal model for old human bone is essential. It is the broad objective of this proposal to explore the use of the ovariectomized (OVX) sheep as a large animal for study of oral bone loss. An advantage of this model is its fidelity to human disease and the potential for measurement of changes in tooth supporting bone and an adjacent edentulous alveolar ridge (within the diastema between molar and incisor teeth) within the same animal and quadrant. Our hypothesis is that estrogen deficiency will result in osteoporosis at both oral and nonoral sites. Our preliminary data suggests that 90 days following ovariectomy, OVX sheep have significantly more sites of periodontitis and more extensive alveolar bone loss than controls. The precise mechanism for this bone loss was not established. The proposed study will assess the incidence and mechanism for oral bone loss in OVX sheep 365 days following ovariectomy and compare the data with sham-operated control sheep. Ovaries will be removed and blood samples obtained at periodic intervals to assess circulating estrogen levels and markers of metabolic bone disease. In addition, teeth will be cleaned, and radiographs obtained. A complete examination of the periodontium will also be done. Animals will receive double fluorochrome labels prior to termination of the experiment. At the end of the experiment, a final periodontal examination will be done, animals will be sacrificed, and jaws, vertebrae, and femurs removed. The mechanical strength of the jaws and bones will also be determined. Bone loss adjacent to teeth will be assessed by histomorphometric evaluation, subtraction radiographic techniques and evaluation of periodontal pocket depths. Gingival inflammation will be assessed by evaluation of histologic sections of gingiva. Bone metabolism will be assessed by study of the distribution of fluorochrome labels in bones. Taken together, this data will suggest 1) whether a relationship exists between estrogen deficiency and oral and systemic bone loss in an animal model with fidelity to human disease, 2) a biologic mechanism for changes in mass and metabolism of bone coincident to ovariectomy, and 3) the specific sites of oral bone loss coincident to ovariectomy.